Due to the increased emphasis on fuel conservation, numerous devices have been proposed for reducing aerodynamic drag on tractor and trailer vehicles so to provide greater fuel efficiency. Normally, these deflectors consist of a rigid device placed atop the tractor cab to streamline the vehicle design at normal highway speeds. These deflectors must be positioned prior to any movement of the vehicle and therefore yield disadvantageous aerodynamic profiles at speeds other than the normal cruising speeds for which they were designed.
Another type of wind deflector has been suggested in the past which is not rigid. These essentially are bag type devices which will deploy on movement of the vehicle. These, however, do not allow any detailed design of their surfaces to provide the best aerodynamic shape available, as may be done using rigid surfaces.
The prior art generally also suffers from the inability of any given design to be easily modified to take into account different heights of trailer units.
To improve upon the above-mentioned types of deflectors and to give other advantages which will become apparent from the following description, the invention was developed.